The present invention relates to laser amplifiers, and more particularly to more efficient energy extraction from laser power amplifiers.
High powered gas lasers have many uses, such as isotope separation research and fusion research. While in general gas lasers are more efficient than other varieties of lasers, such as those employing glass lasing mediums, there is still a great deal of room for improvement in the efficiency of gas laser amplifiers. Exemplarily amplifier gain lasts much longer than the duration of the typical pulse required for isotope separation or fusion. It will be apparent, therefore, that taking advantage of the extra duration of amplifier gain to increase the power output does not increase power input to the laser amplifier, and therefore increases the efficiency considerably.
In many laser systems there is an inherent limitation on a rate at which energy can be extracted. Exemplarily, in CO.sub.2 lasers, excitation of the molecules of CO.sub.2 takes from several tenths of a microsecond to several microseconds, depending on pressure. However, the energy extraction from the upper laser level to the lower laser level in a CO.sub.2 laser is very fast, on the order of tens to hundreds of picoseconds while the CO.sub.2 molecules descend from the lower laser level in approximately six nanoseconds. For laser isotope separation and laser fusion power, a laser pulse on the order of 0.5 nsec is desired. By passing a plurality of pulses through the laser power amplifier, it is possible to reestablish gain in the gas between pulses by allowing molecules to reach the upper laser level and to decay from the lower laser level. The excitation phase can be made faster by employing a higher voltage discharge. However, more energy is consumed, making the process much less efficient. Similarly, the time required by the excited molecules to reach the upper laser level could be made faster by using higher pressures in the gas. However, higher pressure gases incur optically induced breakdown at intensities required for efficient energy extraction, and is still significantly inadequate for efficient energy extraction.